In recent years, a wide variety of types of information are output as records, storage, transmission, and displays to the society. There are a number of output forms of information, and examples thereof include: displays such as CRTs, PDPs, and LCDs; records, storages, and displays on paper (hardcopy) by electrophotographic images such as in copying machines, facsimiles, and printers; and transmissions and displays, for example, by portable telephones or cellular phones and DTAs, and, further, displays of images by electrophoresis of electrifiable black and white colored particles such as PLDs.
Under these circumstances, regarding electrophoresis of electrofiable colored resin fine particles which are electrified within an electrophoretic display cell, electrophoretic display devices are proposed in Japanese Patent Laid-Open No. 185087/1997 (patent document 1), U.S. Pat. No. 3,612,758 (patent document 2), and Japanese Patent Laid-Open No. 249366/2001 (patent document 3). For example, Japanese Patent Laid-Open No. 249366/2001 (patent document 3) proposes an electrophoretic display device which can realize display contrast by simple matrix drive. This publication describes black and white colored electrification electrophoretic fine particles such as polystyrene and polyethylene filled into a cell of a transparent organic insulating liquid such as silicone oil, toluene, xylene, or high-purity petroleum.
Regarding such colored resin fine particles, Japanese Patent Laid-Open No. 89510/2001 (patent document 4) describes acrylic colored resin fine particles (average particle diameter: 0.5 to 100 μm) containing an oil-soluble dye and further discloses colored resin fine particles of, for example, a copolymer of an (meth)acrylic monomer with a styrenic monomer. These colored resin fine particles are prepared by absorbing an acrylic monomer containing an alkyl group such as methyl, ethyl, propyl, butyl, isobutyl, 2-ethylhexyl, lauryl, cyclohexyl, 2-hydroxyethyl, methoxyethyl, or glycidyl, and an oil-soluble dye in seed particles of a polymer with an average particle diameter of 0.05 to 1 μm, prepared, e.g., by emulsion or suspension polymerization using a dispersion of an aqueous medium, such as a (co)polymer of an (meth)acrylic monomer, a styrenic (co)polymer, a copolymer of an (meth)acrylic monomer with a styrenic monomer, and conducting polymerization.
Further, in Japanese Patent Laid-Open No. 243267/1992 (patent document 5), blue, yellow, red or other dye-containing colored resin particles, with a particle diameter of 6 to 8 μm, of a styrene-(meth)acrylic copolymer of styrene with methyl acrylate, n-butyl methacrylate, 2-ethylhexylmethacrylate are described as toner particles for electrostatic image development. These particles are proposed as resin particles that exhibit charging characteristics of −25 to −30 (μc/g) in terms of amount of electrification as measured by the blow-off method. These particles are prepared by adding thermoplastic resin particles, prepared by polymerization and growth according to a seed polymerization method or a suspension polymerization method, in a system of a dye as a colorant dissolved in an alcoholic solvent to color the resin particles with the dye.
Japanese Patent Laid-Open No. 42683/1989 (patent document 6) describes a particle rotation-type display device. The rotation particles for display which have two separated color regions disclosed in this document are prepared by adding titanium oxide to wax, granulating the mixture by a spray drier method, classifying the particles, and then spraying, for coloring, a carbon black-dispersed alkyd resin enamel onto the hemispherical surface of white wax particles with an average particle diameter of 50 μm. A green pigment is dispersed in wax, a red pigment is dispersed in wax, and a blue pigment is dispersed in wax. The green pigment-dispersed wax, the red pigment-dispersed wax, and the blue pigment-dispersed wax were granulated to prepare respective particles. These particles are classified to prepare green particles with an average particle diameter of 30 to 150 μm, blue particles with an average particle diameter of 30 to 150 μm, and red particles with an average particle diameter of 30 to 150 μm which are then dispersed in RTV rubber. The rubber mass is subjected to color separation while heating at 90° C. under centrifugal force. After cooling, color separated display particles are recovered from thinly cut rubber.
Japanese Patent Laid-Open No. 352421/1999 (patent document 7) discloses a process for producing two-color color separated display rotation particles for use in display of PLDs and the like. In this production process, different color layers are formed on hemispherical surfaces of microballs by a thin-film preparation method such as a vacuum deposition method, a sputtering method, a chemical vapor deposition method, or a spinner coating method.
Japanese Patent Laid-Open No. 122103/2000 (patent document 8) describes rotatable electrifiable electrophoretic color balls of two colors of black and white provided within microcapsules. These two-color balls are prepared by preparing white titanium dioxide-filled glass beads and plastic beads and then vacuum-depositing a mixture of antimony sulfide with magnesium fluoride as a black material onto the hemispherical surfaces.
[Patent document 1] Japanese Patent Laid-Open No. 185087/1997
[Patent document 2] U.S. Pat. No. 3,612,758
[Patent document 3] Japanese Patent Laid-Open No. 249366/2001
[Patent document 4] Japanese Patent Laid-Open No. 89510/2001
[Patent document 5] Japanese Patent Laid-Open No. 243267/1992
[Patent document 6] Japanese Patent Laid-Open No. 42683/1989
[Patent document 7] Japanese Patent Laid-Open No. 352421/1999
[Patent document 8] Japanese Patent Laid-Open No. 122103/2000